This application is based on and claims priority to Japanese Patent Application No. Hei 11-318549, filed Nov. 9, 1999, the entirely of which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to a control system for an engine, and more particularly to an apparatus and method for calibrating a throttle valve sensor in the control system.
2. Description of the Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, increasing power output. Efforts are being made to maximize the performance of individual engine systems in order to maximize overall engine performance.
Control systems are currently employed to control the various aspects and systems of the engine, such as air intake, fuel injection, timing, etc. Sensors are provided at various locations throughout the engine. These sensors detect specific engine conditions and transmit an electronic signal indicative of such conditions to an electronic control unit xe2x80x9cECU.xe2x80x9d The ECU controls the engine systems in response to inputs from the sensors. For instance, in some configurations, an engine speed sensor and a throttle valve position sensor are provided and respective signals from these sensors are used by the ECU to determine suitable fuel amounts during operation of the engine. The desired fuel amounts for specific conditions can be defined in a control map stored in the ECU and can depend upon both engine speed and throttle valve position.
Faulty sensor data can confuse the ECU and/or can cause the ECU to control the engine in a manner that does not maximize performance. It is thus important to obtain accurate sensor readings. However, due to errors during sensor assembly and to variations in power voltage, there is often a deviation between an actual throttle opening angle and a throttle opening angle detected by the throttle opening sensor. Because the ECU determines control based upon this erroneous reading, the ECU may direct delivery of fuel in amounts that do not optimal engine performance for the giving engine running conditions. Also, the ECU may not be able to correctly determine when the throttle valve is in the idle state.
The present invention involves the recognition of the above-stated problem and the further recognition that better engine control can be achieved by having the engine control system compensate for the inaccuracies in the sensed throttle valve positions due to errors during sensor assembly and to variations in power voltages.
One aspect of the present invention thus an internal combustion engine with an engine control system. The internal combustion engine includes a cylinder block defining at least one cylinder bore. A piston reciprocates within the cylinder bore. A cylinder head closes an end of the cylinder bore to define a combustion chamber together with the cylinder bore and the piston. An air induction system is arranged to introduce air to the combustion chamber. The air induction system includes an air intake passage and a throttle valve, and the control system includes a throttle valve opening sensor and a control unit. The control unit controls at least one fuel injector. The throttle valve is moveably disposed within the air intake passage and admits air in proportion to an opening degree thereof. The throttle valve opening sensor is arranged to sense the opening degree and to output a signal indicative of the opening degree to the control unit. The fuel injector is arranged to supply fuel to the combustion chamber. The control unit is configured to determine an amount of fuel to be supplied at least based upon the opening degree signal. The control unit has a memory having an actual opening degree of the throttle valve at an engine idle position stored therein and having a correction value stored therein. The control unit is further configured to determine the correction value as a difference between the stored actual opening degree of the throttle valve at engine idle and an opening degree signal sensed by the throttle valve opening sensor at engine idle.
Another aspect of the present invention involves a method for controlling an engine. The engine includes a fuel injector, an air intake passage having a throttle valve, a throttle valve opening sensor, and a control unit having a memory. The throttle valve is movable between an idle position and a second position. The throttle valve opening sensor is adapted to sense the opening degree and to output a signal indicative of the opening degree to the control unit. An actual opening degree of the throttle valve at the idle position is precisely measured and is then stored in the memory. The throttle valve opening sensor senses the throttle valve opening degree when the throttle is at the idle position and sends an idle opening degree signal to the control unit. A correction value is determined by computing the difference between the stored actual idle opening degree and the sensed idle opening degree signal. The correction value is stored in the memory. An adjusted throttle opening degree is determined by applying the correction value to the opening degree signal from the throttle valve opening sensor.
Further aspects, features, and advantages of this invention will become apparent from the detailed description of the preferred embodiment which follows.